I got the new piece home and put it alongside the other one. Hmmm, the bits I thought were bigger are actually the same size on each lens!
When I was messing around with it I found the rear turret tube (or whatever one might like to call it) is loose in the body and can slide out. I am not sure if this is a fault or some macro facility! Nothing to indicate the later.
I contacted the previous owner who said it came from his uncle who was a telescope technician at an observatory so I guess I should not be suprised to come across the odd 'modification'!
The teleconverter thing is apparently 8x ! No wonder I could not focus it, it is effectively 4000mm f32! I will be putting that aside until I get an adapter made for my equatorial telescope mount then we might see some space images! Meanwhile I think I will need to have an adapter made to mount my camera, it should be a simple metal turning job and a K mount adapter screwed on the end. Unfortunately I dont have the skills or tools for that job but at least I have pieces on the other lens to measure.
Considering the marking on the TC I guess it was originally intended to be fitted to something like a 120mm F2(?).
I am alsoconsidering treating this new one to a professional clean and align, I know a man who does a good job at a reasonable price.
So what can I do with two of these? A stereo camera? Monster binoculars? Could I join the light paths and make a 500mm f2?:G